Resistance development,cross-resistance,and fitness costs associated with Aphis gossypii resistance towards sulfoxaflor and acetamiprid in different geographical regions

Aphis gossypii has become increasingly difficult to manage due to its strong insecticide resistance.In the laboratory,we established sulfoxaflor-resistant and acetamiprid-resistant strains in two A.gossypii populations with different basal insecticide resistance levels,and evaluated the effects of basal insecticide resistance on the resistance development and cross-resistance,as well as differences in fitness.Under the same selection pressure,Yarkant A.gossypii(with low basal insecticide resistance)evolved resistance to sulfoxaflor and acetamiprid more quickly than Jinghe A.gossypii(with high basal insecticide resistance),and the evolution of A.gossypii resistance to sulfoxaflor developed faster than acetamiprid in both Yarkant and Jinghe,Xingjiang,China.The sulfoxaflor-resistant strains selected from Yarkant and Jinghe developed significant cross-resistance to acetamiprid,imidacloprid,thiamethoxam and pymetrozine;while the acetamiprid-resistant strains developed significant cross-resistance to sulfoxaflor,imidacloprid,thiamethoxam,pymetrozine,and chlorpyrifos.The relative fitness of A.gossypii decreased as the resistance to sulfoxaflor and acetamiprid developed.The relative fitness levels of the sulfoxaflor-resistant strains(Yarkant-SulR and Jinghe-SulR)were lower than those of the acetamipridresistant strains(Yarkant-AceR and Jinghe-AceR).In addition,the relative fitness levels of sulfoxaflor-and acetamiprid-resistant strains were lower in Jinghe than in Yarkant.In summary,basal insecticide resistance of A.gossypii and insecticide type affected the evolution of resistance to insecticides in A.gossypii,as well as cross-resistance to other insecticides.The sulfoxaflor-and acetamiprid-resistant A.gossypii strains had obvious fitness costs.The results of this work will contribute to the insecticide resistance management and integrated management of A.gossypii.

Lack of fitness cost and inheritance of resistance to abamectin based on the establishment of a near-isogenic strain of Tetranychus urticae

Many populations of the two-spotted spider mite, Tetranychus urticae Koch, have developed high levels of resistance to the pesticide abamectin in China and other countries. This study developed a near-isogenic line to understand better the inheritance, cross-resistance, and fitness costs associated with abamectin resistance in the field population of T. urticae in China. We introduced the trait that confers extremely high abamectin resistance in a field-collected population of T. urticae into a susceptible laboratory strain(IPP-SS) to generate an abamectin-resistant near-isogenic line(NIL-Aba).This process was carried out through multiple backcrossing to IPP-SS and via parthenogenesis and abamectin screening. Compared with IPP-SS, the NIL-Aba strain had a 25 147-fold resistance to abamectin and a high level of cross-resistance to bifenthrin(288.17-fold), an intermediate level to emamectin benzoate(42.57-fold), and low levels to bifenazate, chlorfenapyr, cyflumetofen, cyenopyrafen, and cyetpyrafen with resistance ranging from 3.18-to 9.31-fold.But it had no cross-resistance to profenofos. The resistance to abamectin in NIL-Aba was autosomal, incompletely dominant, and polygenic. Based on two sex life table parameters, no fitness cost was found in NIL-Aba. Establishing the NIL-Aba strain provides a reliable basis for an in-depth study of abamectin resistance in T. urticae. New information on toxicological characteristics and fitness cost should facilitate the management of abamectin resistance in field populations of T. urticae.

Genetics and fitness costs of resistance to flupyradifurone in Bemisia tabaci from China

Flupyradifurone is a promising new insecticide used for controlling Bemisia tabaci during vegetable production.In this study,we assessed the fitness costs and mode of inheritance associated with resistance to flupyradifurone in B.tabaci by comparing the susceptible strain(MED-S)to one field-evolved flupyradifurone-resistant strain(WH-R,with 199-fold resistance)and one laboratory-selected flupyradifurone-resistant strain(FLU-SEL,with 124-fold resistance).Progenies of reciprocal crosses between WH-R and MED-S(F_(1A),F_(1B),and pooled F_(1)),and between FLU-SEL and MED-S(F_(1C),F_(1D),and pooled F_(1)’),showed varying degrees of dominance,indicating that resistance to flupyradifurone in WH-R was autosomal and incompletely dominant,yet in FLU-SEL it was autosomal and incompletely recessive.Furthermore,the development of resistance to flupyradifurone occurred at the expense of fitness costs for the resistant populations.Compared to the MED-S strain,WH-R showed a relative fitness of 0.50 with significantly prolonged developmental durations and reduced survival rates of the nymphal and pseudopupal stages,as well as decreased fecundity and hatchability.Similarly,FLU-SEL showed a relative fitness of 0.65 and also demonstrated prolonged developmental durations and reduced survival rates of nymphs and pseudopupae,as well as decreased hatchability in comparison with the MED-S strain.However,no significant differences in fecundity were observed between MED-S and FLU-SEL.The present study provides useful knowledge for formulating pest management strategies in the field,which will allow growers to slow the development of resistance to flupyradifurone and to sustainably control B.tabaci.

Energy Intensity and Fitness Cost of Cotton aphid Exposure to Neonicotinoids

Three populations of Aphis gossypii of distinct susceptibility to neonicotinoids show differences in the accumulation and mobilization of energy reserves, what may allow the production of their defensive tools against two neonicotinoid insecticides without impairing their reproductive performance. Bioassays were also carried out for these aphid populations. According to the results obtained, the Ag-R population showed resistant rate significantly higher than the other two populations. Levels of some biochemical characteristics were determined in the resistant, susceptible and semi susceptible populations of cotton aphid. The results obtained in the assays with biochemical parameters indicated significant differences in activity among the populations, with higher activity in using glycogen in the Ag-R population. The inverse activity trends oft （generation time） and DT （doubling time） in both resistant and susceptible populations, one showing fitness disadvantage without insecticide exposure and the other not showing it, may underlay the mitigation of insecticide resistance physiological costs observed in the Ag-R population.

Risk assessment,fitness cost,cross-resistance,and mechanism of tetraniliprole resistance in the rice stem borer,Chilo suppressalis

The rice stem borer(RSB),Chilo suppressalis,a notorious rice pest in China,has evolved a high resistance level to commonly used insecticides.Tetraniliprole,a new anthranilic diamide insecticide,effectively controls multiple pests,including RSB.However,the potential resistance risk of RSB to tetraniliprole is still unknown.In this study,the tetraniliprole-selection(Tet-R)strain was obtained through 10 continuous generations of selection with tetraniliprole 30%lethal concentration(LC_(30)).The realized heritability(h^(2))of the Tet-R strain was 0.387,indicating that resistance of RSB to tetraniliprole developed rapidly under the continuous selection of tetraniliprole.The Tet-R strain had a high fitness cost(relative fitness=0.53).We established the susceptibility baseline of RSB to tetraniliprole(lethal concentration at LC_(50)=0.727 mg/L)and investigated the resistance level of 6 field populations to tetraniliprole.All tested strains that had resistance to chlorantraniliprole exhibited moderate-to high-level resistance to tetraniliprole(resistance ratio=27.7-806.8).Detection of ryanodine receptor(RyR)mutations showed that the Y4667C,Y4667D,I4758M,and Y4891F mutations were present in tested RSB field populations.RyR mutations were responsible for the cross-resistance between tetraniliprole and chlorantraniliprole.Further,the clustered regularly interspaced palindromic repeats(CRISPR)/CRISPR-associated protein 9-mediated genome-modified flies were used to study the contribution of RyR mutations to tetraniliprole resistance.The order of contribution of a single RyR mutation to tetraniliprole resistance was Y4667D>G4915E>Y4667C~~I4758M>Y4891F.In addition,the I4758M and Y4667C double mutations conferred higher tetraniliprole resistance than single Y4667C mutations.These results can guide resistance management practices for diamides in RSB and other arthropods.

Resistance and fitness costs in diamondback moths after selection using broflanilide, a novel meta-diamide insecticide

The diamondback moth (DBM) Plutella xylostella (L.) (Lepidoptera: Plutellidae) is an insect pest found around the world that feeds on cruciferous crops. The DBM has become resistant to most insecticides in current use in the field. Broflanilide is a novel meta-diamide insecticide that binds to a new site on the γ-aminobutyric acid receptor and very efficiently protects against most pests in the order Lepidoptera, including DBM. In this study, the resistance of a laboratory-bred susceptible strain of DBM to broflanilide and the fitness costs posed by broflanilide to the DBM were evaluated. The DBM had no obvious resistance to broflanilide after 10 generations of selection. The realized heritability h2 was 0.033, suggesting a low risk of resistance developing in this strain. The F10 generation had no cross-resistance to the insecticides abamectin and endosulfan (which target the γ-aminobutyric acid receptor) and chlorantraniliprole (which targets a non-γ-aminobutyric acid receptor). The specific activities of important detoxification enzymes (cytochrome P450 monooxygenase, esterase, and glutathione S-transferase) were not obviously altered. However, the larval stage was prolonged and the adult stage was shortened significantly in F11 generation than the F0 generation. The total preoviposition period TPOP significantly prolonged 1.90 d in F11 generation. The fitness value Rf (0.93) was lower for the F11 generation than the F0 generation. The results indicated that long-term exposure to broflanilide exerts clear fitness costs in the DBM. This information will be useful in identifying reasonable broflanilide application guidelines for managing broflanilide resistance in the DBM.

Effects of temperature on fitness costs in chlorpyrifos-resistant brown planthopper, Nilaparvata lugens （Hemiptera： Delphacidae）

Insecticide resistance is inevitable if an insecticide is widely used to control insect pests. Fortunately, the resistance-associated fitness costs often give chances to manage resistances. In most cases, the fitness cost in resistant insects is often evaluated under laboratory conditions for insect development, which limits its practical application in pest control in the field. In a laboratory population R9 with 253-fold resistance to chlorpyrifos after nine-generation selection with chlorpyrifos, the relative fitness was only 0.206 under laboratory conditions （25℃, humidity 70%-80% and 16 h light/8 h dark photoperiod）, when compared to S9, a susceptible counterpart （resistance ratio = 2.25- fold） from the same origin as R9 but without any selection with insecticides. Temperatures varied the resistance-associated fitness costs, with enhanced costs at high temperatures and reduced costs at low temperatures, such as 0.174 at 32℃ and 0.527 at 18℃. The copulation rate and fecundity were two key factors for the reduced costs at low temperatures. Another finding was that R9 individuals needed much more time to recover from heat shock than that of S9, but R9 and $9 individuals were similarly sensitive to cold shock. The low fitness cost at low temperatures would increase the overwintering population, which might further increase risks of rapid development and widespread distribution of chlorpyrifos resistance in Nilaparvata lugens.

Relative fitness of susceptible and Cry1A.105/Cry2Ab2-single-/dual-protein-resistant Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) on non-Bt diet and a diet containing a low concentration of two proteins

Helicoverpa zea(Boddie)is a destructive agricultural pest species that is targeted by both Bacillus thuringiensis(Bt)maize and cotton in the United States.Cry1A.105 and Cry2Ab2 are two Bt proteins expressed in a widely planted maize event MON 89034.In this study,two tests(Test-Ⅰ and Test-Ⅱ)were conducted to evaluate the relative fitness of Bt-susceptible and-resistant H.zea on non-Bt diet(Test-Ⅰ and Test-Ⅱ)and a diet containing a mix of Cry1A.105 and Cry2Ab2 at a low concentration(Test-Ⅱ only).Insect populations evaluated in Test-Ⅰ were two Bt-susceptible strains and three Bt-resistant strains(a single-protein Cry1A.105-,a single-protein Cry2Ab2-,and a dual-protein Cry1A.105/Cry2Ab2-resistant strains).Test-Ⅱ analyzed the same two susceptible strains,three backcrossed-and-reselected Cry1A.105/Cry2Ab2-single-/dual-protein-resistant strains,and three F1 heterozygous strains.Measurements of life table parameters showed that neither the single-nor dual-protein Cry1A.105/Cry2Ab2 resistance in H.zea was associated with fitness costs under the test conditions.The single Cry protein resistances at a concentration of a mix of Cry1A.105 and Cry2Ab2 that resulted in a zero net reproductive rate for the two susceptible strains were functionally incomplete recessive or codominant,and the dual-protein resistance was completely dominant.The lack of fitness costs could be a factor contributing to the rapid revolution of resistance to the Cry proteins in this species.Data generated from this study should aid our understanding of Cry protein resistance evolution and help in refining IRM programs for H.zea.

A meta-analysis of the effects of geolocator application on birds

An increasing trend in use of tracking devices such as geolocators is based on the assumption that the information gathered from such devices provides reliable information about the migratory behavior of free-living birds. This underlying as- sumption is rarely tested, as evidenced by the absence in many studies of controls, in particular treated controls, and so far never with a reasonable statistical power. Published studies have shown reduced survival prospects or delayed breeding in some species, suggesting that there may be reason to doubt that tracking devices provide unbiased information. Therefore, we conducted a meta-analysis of studies applying geolocators to wild birds to determine whether geolocators affected fitness components. Ge- olocators had an overall negative effect on fitness components, in particular survival, and ecological variables. Effect size was larger for aerial foragers than for other species. Moreover the leg band attachment method was more detrimental for birds than the leg-loop backpack harness. A meta-regression model of effect size showed independent negative effects of geolocators on ae- rial foragers, smaller species, species with smaller migration distances and in studies where geolocators were attached with a ring. These results suggest that geolocator studies should be interpreted with caution, but also raise questions whether it is ethically defensible to use geolocators on aerial foragers or small species without carrying out robust pilot studies.

Offspring diet supersedes the transgenerational effects of parental diet in a specialist herbivore Neolema abbreviata under manipulated foliar nitrogen variability

Diet quality influences organismal fitness within and across generations.For herbivorous insects,the transgenerational effecets of diet remain relatively underexplored.Usinga3×3×2 factorial experiment,we evaluated how N enrichment in parental diets of Neolemd abbreviata(Larcordaire)(C oleoptera:Chrysomelidae),a biological control agent for Tradescantia fluminensis Vell.(Commelinaceae),may influence life history and performance of Fi and F2 offspring under reciprocal experiments.We found limited transgenerational effects of foliar nitrogen variability among life-history traits in both larvae and adults.Larval weight gain and mortality were responsive to parental diet contrary to feeding damage,pupal weight and duration taken to pupate.There were significant parental diet x test interactions in larval feeding damage,weight gain,pupal weight and time to pupation.Generally,offspring from parents under high N plants performed better even under low N test plants.Adult traits including oviposition selection,feeding weight and longevity did not respond to the efects of parental diet nor its interaction with test diet as was the case in the larval stage.However,the main efects of test diet were more important in determining adult performance in both generations suggesting limited sensitivity to parental diet in the adult stage.Our results show conflicting responses to parental diet between larvae and adults ofthe same generation among an insec species with both actively feeding larual and adult life stagee These tranegeneratinonal efferte,or lack thereof,may have implications on the field performance of N.abbrevita under heterogencous nutritional landscapes.

No trade-off between trichome production and tolerance to leaf and inflorescence damage in a natural population of Arabidopsis lyrata

Aims Early models of plant defense conceived resistance and tolerance to herbivore damage as mutually exclusive strategies.support for this idea has been equivocal and studies on these two strategies are still needed to understand the evolution of defenses in natural populations.In Arabidopsis lyrata,the production of trichomes,a documented resistance trait,has been associated with a fitness cost in the absence of herbivores.We examined whether trichome production is also associated with reduced tolerance to simulated herbivore damage.Methods We conducted a field experiment in a natural swedish population of A.lyrata where we inflicted leaf(0 vs.50%of the area of each leaf removed)and inflorescence damage(0 vs.50%of inflores-cences removed)to trichome-producing and glabrous plants in a factorial design.We examined the response(survival,growth and reproduction)of the plants to the imposed damage over 2 years.Important Findingstrichome-producing plants were not less tolerant than glabrous plants to simulated herbivore damage(no significant morph×leaf damage or morph×inflorescence damage interactions).Inflorescence and leaf damage had independent negative effects on the performance of damaged plants.leaf damage reduced rosette size the year of damage,but effects on reproductive output in the year of damage,and on survival and reproductive performance the following year were weak and not statistically significant.Inflorescence damage significantly reduced the number of flowers,fruits and seeds the year of damage,but not in the following year.Irrespective of morph,the study population was more tolerant to leaf than to inflorescence damage.the results indicated no trade-off between trichome production and tolerance,suggesting that these two defense mechanisms have the potential to evolve indepen-dently in this A.lyrata population.